The invention relates to a device for transferring a material in the form of a film applied to a carrier strip onto a substrate, such as a sheet of writing or drawing paper, comprising a housing in which a supply reel for the film-coated carrier strip and an empty reel for receiving the de-coated carrier strip are arranged, wherein the film-coated carrier strip is guided over an applicator foot provided at least in the region which is looped around by the carrier strip with a clip-type slide element of a friction-reducing material secured to the applicator foot.
Hand devices of that kind for transferring a film (for example, adhesive strip, concealing substance, marking ink, etc.) are known. In that case, in order to achieve a smooth motion and good capability of transfer of the film onto the substrate various embodiments for the shapes of the applicator foot are known. Thus, the applicator foot can be equipped with, for example, an applicator roller which preferably has a rubber-elastic running surface. However, as the external diameter of a functionally effective applicator roller cannot be kept as small as desired, because a good adaptation to the substrate requires a minimum thickness for the elastic running ring and the rotational mobility presupposes a sufficient difference between axle stub and external diameter, such an applicator roller has disadvantages. Accordingly, in most solutions the applicator foot usually has an applicator strip which has advantages relative to an applicator roller, as a sharper angling of the carrier strip is possible in the transfer phase, whereby the torn-off piece has less tendency to formation of a wavy edge after completion of the transfer. Thereagainst it is disadvantageous relative to the applicator roller solution that in the case of the applicator strip the carrier strip is guided thereover with a friction couple which, in dependence on the respective carrier strip quality, can lead to undesired heavygoing.
In principle, synthetic materials which have a good sliding property are known, for example polytetrafluorethylenes (PTFE), but which are higher in cost by a multiple than the standard materials usually used for the components of a device of the kind in question.
Accordingly, the use of an applicator foot of polytetrafluorethylene is excluded on cost grounds.
As polytetrafluorethylene is not a true thermoplastic, a loading of the region, which is effective with respect to guidance, of the applicator foot by this high-quality material in a multi-component injection-moulding process or a subsequent injection-moulding process has to be excluded. A conceivable solution, such as gluing the applicator strip by a self-adhesive foil coated with fluoro synthetic material, has in fact been attempted already, but from the viewpoint of production engineering is unsuitable for mass-produced articles.
A device of the category in question is known from U.S. Pat. No. 5,430,904. In this device the applicator foot is provided in the region which is looped around by the carrier strip with a slide element made of a friction-reducing, rubber-elastic material and fastened to the applicator foot. This slide element is to serve the purpose of achieving faultless transfer of the film onto the substrate. However, it has proved that the smooth motion of the device and the transfer of the film to the substrate is still capable of improvement.
It is accordingly the object of the invention to so improve a device according to the category that the smooth motion of the device and faultless transfer of the film onto the substrate are guaranteed in return for smallest possible use of material and with particular consideration of economic capability of manufacture and possibility of assembly.
In accordance with the invention this object is met in the case of a device of the kind denoted in the introduction in that the applicator foot comprises a pivotably hinged extension arm having at the end a receiving profile member (end portion) for the slide element.
On the one hand, due to this construction there is achieved, within certain limits, a more flexible articulation of the applicator strip with the slide element at the applicator foot, whereby a better transfer of the film is achieved even to a not completely flat substrate. On the other hand, the clip-type slide element can be mechanically pushed in simple manner onto the extension arm in the pivoted-out position thereof after a spreading process and can be securely fastened to the applicator foot by pivoting in and locking of the arm.
The slide element itself can be produced from, for example, a polytetrafluorethylene tube as a semi-finished product of the smallest dimensions (for example, with an external diameter of 1 to 1.2 millimetres and 0.2 to 0.3 millimetres wall thickness), in that it is cut off to the desired length, slit in longitudinal direction and then spread apart and pushed onto the applicator foot. This can be carried out automatically in simple manner.
In an advantageous embodiment it is provided that the extension arm is securable to the applicator foot in the pivoted-in position by means of a detent connection. After the automatic pushing on of the clip-type slide element the extension arm can then be mechanically pivoted in and then automatically locked to the applicator foot in the pivoted-in position. Moreover, it is, with advantage, provided that abutment steps for securing against twisting and recesses for securing against longitudinal displacement of the clip-type slide element are provided at the applicator foot and/or extension arm.
In order to further facilitate handling of the device it is proposed that the extension arm is provided with longitudinally oriented ribs. These ribs serve, preferably in conjunction with selection of an elastic materialxe2x80x94for example, a polyolefinxe2x80x94for the extension arm, for ensuring contact between the applicator foot and possible unevennesses of the substrate plane. As the slide element is similarly elastic, it is thus achieved that even in the case of a non-planar substrate the entire transfer width is acted on by pressure and, in similar manner to an elastic roller, formation of bubbles is prevented.
With particular advantage it is proposed in that case that the ribs rise in wedge-shaped manner starting from the slide element and each have a rear wall which in the pivoted-in position of the extension arm bears against a respective abutment of a cross-member of the applicator foot. In this manner it is possible to bias the ribs in a specific way in the pivoted-in position of the extension arm so as to ensure a bubble-free transfer of the film to the substrate in the case of a non-planar substrate.
In that case it is proposed with particular advantage that the prism-shaped abutments are so constructed that they together form an approximately arcuate support profile for the rear walls of the wedge-shaped ribs. It is thus achieved that the ribs are biased to increasingly greater extent towards the middle of the extension arm and in consequence thereof the slide element describes a spherical course relative to the substrate plane, so that even in the case of a non-planar substrate a sufficient application pressure for a bubble-free transfer is achieved over the entire transfer width.
In order to be able to carry out production of the device in particularly simple manner, i.e. automatically, there is also proposed in accordance with the invention a method for production of the device in which a supply reel with a film-coated carrier strip and an empty reel are inserted into the housing of the device, wherein the method is distinguished by the fact that for formation of the clip-type slide element a tube section of friction-reducing material is located and held, is slit in longitudinal direction and is pushed, while being spread apart, onto the applicator foot or the extension arm.
In that case, for example, a polytetrafluorethylene tube can be fed as a semi-finished product of smallest dimensions, for example with an external diameter of 1 to 1.2 millimetres and a wall thickness of 0.2 to 0.3 millimetres, to an automatic machine, cut to length there, slit mechanically or by another cutting technique, such as laser or water jet cutting, in longitudinal direction and subsequently spread apart by means of a conical holding mandrel to the required assembly profile, whereupon the clip-type slide element is then laterally stripped off onto the applicator foot or the extension arm of the applicator foot.
For carrying out this above-described process there is provided a device which is distinguished by a gripper-like holding device for the tube section, a conical retaining mandrel and a cutting device.